Individual species have ranges that limit where they live–not all species are found everywhere. For over a century, naturalists and ecologists have worked to discern what governs the limits of those ranges, and therefore determines what species are in a given location or where a species might be found. This field is known as “biogeography” and it demonstrates the intricate linkages between ecology and evolutionary biology. The most obvious foundations for this field of study were set down by Darwin during his voyage on the Beagle (seeing all the different organisms spread across the globe helped to get him thinking about his theory of evolution by natural selection), as well as by Alfred Russel Wallace, a less well-known contemporary of Darwin’s who independently and near-simultaneously came up with the theory of evolution of species while studying birds in New Guinea (Wallace even has an imaginary boundary named after him that separates the very different organisms of Asia from those of the Australian and New Guinean areas).

Questions about what limits species ranges aren’t limited to organisms like birds, trees or mammals, though. Part of the work we do down here is looking at what controls the ranges of the species of soil animals we find, and how long those animals have been where they are. In order to do this, we have to get out of Taylor Valley (where most of our work, such as the LTER, is carried out) and collect samples from the other valleys and areas of exposed soils (such as nunataks, or mountaintops that stick out from glacial cover). When we do this, our aim is to try and cover a variety of different habitat conditions, such as available moisture, visible mosses, algae or lichen, the amount of salts in the soil, size of the soil particles, how much exposure to sun the area gets and other factors that may influence how habitable different places in the valley are, which can inform us as to why we do or don’t find certain species in a given location. Last year, Byron, Uffe, Diana and Ian Hogg (our colleague from Waikato University in New Zealand) were able to get down to the Beardmore glacier and collect samples at many different locations there, which is much further south than the Dry Valleys. This year, we were fortunate enough to have Ian and Jeb Barrett (another of our colleagues, from Virginia Tech) send us samples from this region again; in addition, a group of New Zealand researchers led by Craig Carey have been sending us samples from some of the more southern Dry Valleys such as Miers and Hidden Valley.

This year, Byron, Uffe and Zach were able to get to some less-visited parts of the Dry Valleys to collect samples. They first started by going to Mount Suess, which is further north in the Transantarctic Mountains than Taylor Valley. Mount Suess sticks up out of the surrounding Mackay Glacier, and has a lower ridge that projects from the east side of the mountain. This ridge is covered with soil and dotted with small meltponds, which harbor mats of algae and patches of moss. Here you can see a picture of the mountain, with the soil-covered ridge in the foreground.

And here is a picture of one of the small ponds.

The three of us each went a different way from the helicopter, while the pilot stayed by the helicopter for our return. Each of us had a radio so that we could check in periodically, and to make sure we were all okay–if something happened to one of us, we could let the others know. Uffe went downhill and sampled by some of the meltponds and surrounding area while Zach moved along a small rocky ridge and Byron moved along the top of the ridge toward some other small ponds. Below you can see an example of one of the patches of soil we sampled, and note the small patches of green moss along the bottom of the rocks in the top-center!

We spent an hour and a half on the ground here collecting samples, and then got back into the helicopter to travel to Wall Valley, named after our own Diana Wall! Wall Valley was a short 30 minute flight west and slightly south of Mount Suess, and we passed over some pretty stunning areas that make you realize how big the Dry Valleys are, as you can see here:

Right before we got to Wall Valley, we passed Virginia Valley, named after Ross Virginia, from Dartmouth College, whom Diana has worked down in Antarctica with for over 20 years! As we made our approach, we got a picture of Wall Valley:

Previous sampling at Wall Valley by the Wormherders wasn’t successful in recovering nematodes, as the soil down at the bottom of the valley is too high in salts, which the nematodes can’t tolerate. So this time, we went up along the edge of the valley, sampling in the scree piles that slope up along the valley’s walls. Here you can see the helicopter on the valley floor, and up to the top right stretches a scree slope that Uffe has gone up to sample:

Again, we collected samples for an hour and a half and then made our way back to the helicopter to travel to our last destination, Hawkins’ Cirque. The Cirque, named after the head helicopter pilot at McMurdo, is a small hemisphere-shaped break in the wall of Wright Valley, and sits nearly all the way back in the valley just above the glacier. Here you can see across the Cirque, with the glacier to the left:

After we finished collecting samples, we posed for a group photo: from left to right are Uffe, Byron and Zach.

Once we’ve extracted and had a chance to examine these samples under the microscope, we can look at these data together with the data from other samples collected by ourselves and our colleagues, and begin to put together a better picture of what governs why we find species of soil animals where we do in the Dry Valleys. By looking at overall patterns in distributions, and through use of several dating tools (both by examining age of the exposed rock surfaces as well as comparing the times that different populations of animals in different areas may have been separated by, using molecular genetics), we can start to explain how dispersal throughout the valleys may have occurred, and why some areas were colonized while others were not!

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